The present invention generally relates to a method of manufacturing a thermoplastic encapsulated wire rope, and more specifically, to a method of quenching such thermoplastic encapsulated wire rope in a lubricant bath or spray to fill any openings in the thermoplastic with lubricant and to the encapsulated rope so produced.
The wire rope of the present invention usually will comprise lubricated strands encapsulated in a thermoplastic or an elastomer. Patents relating to such thermoplastic impregnation of wire ropes include U.S. Pat. Nos. 3,824,777 and 3,874,158. The individual wire strands are lubricated in an extrusion process with a conventional lubricant such as petrolatum at about room temperature, or with an asphaltic based lubricant which is applied at about 150.degree. F. (65.degree. C.). The lubricated strand rope is then thermoplastic encapsulated in an extrusion operation. The rope is heated to 150.degree.-300.degree. F. (51.degree.-150.degree. C.) and is passed through an extrusion die wherein the thermoplastic is injected into the rope, extending to the inner rope and between inner rope strands and outer rope strands and between outer rope strands. Such thermoplastic encapsulation inhibits the entrance of foreign abrasive particles into the rope, seals the lubricant within the rope for optimal lubrication life, minimizes rope metal to outside metal contact for increased rope strength and life, and locks the component strands in their respective fabricated positions to provide increased resistance to strand expansion such as popping or bird caging.
However, thermoplastic or elastomer encapsulation of the wire rope may actually promote corrosion if all possible interstices between rope strands are not filled either with a plastic, an elastomer or a lubricant. If not so filled, such interstices can entrap moisture within the rope and lead to corrosion.
The present invention accordingly provides a method of quenching the fully thermoplastic or elastomer encapsulated wire rope with a heavy fluid lubricant such as a petrolatum based, mineral based or combination thereof. When the lubricated rope exits the extrusion die first after thermoplastic or elastomer encapsulation, the rope is at about 150.degree.-300.degree. F. (51.degree.-149.degree. C.). When entering the quench bath trough or spray, being at 50.degree.-100.degree. F. (10.degree.-38.degree. C.), the wire rope cools very rapidly. Such cooling creates a vacuum within the interstices of the rope which causes the quenching lubricant to be drawn into the rope through any opening in the thermoplastic or elastomer coating.
The wire rope of the present invention could be of a swaged construction whereby a thermoplastic or an elastomer could be placed around the interior rope strands. The outer rope strands could then be wound around such thermoplastic or elastomer, and the entire rope then either roller or die compacted to embed the outer strands into the thermoplastic or elastomer. A patent relating to such outer strand compaction is U.S. Pat. No. 4,120,145.